In the field of polymer production, silylated polymers are generally known to be useful as components of coatings, adhesives, sealants and other elastomeric products. The production of these silylated polymers can be by a continuous or batch process and generally includes a silylation step, where a prepolymer is reacted with a silylating agent in a silylation reaction to produce a silylated polymer composition. Often times, this silylation reaction does not proceed to completion. An incomplete silylation reaction usually leads to deterioration in the produced silylated polymer. For example, the more incomplete the silylation reaction, the more unreacted reactive groups will remain in the silylated polymer composition. These unreacted reactive groups continue to react in the silylated polymer composition. Properties observed immediately after the formation of the silylated polymer composition do not remain constant. For example, reaction of the unreacted reactive groups over time can cause viscosity creep which changes the viscosity of the produced silylated polymer over time. This change in viscosity will be referred to herein as viscosity creep.
While there have been valiant attempts to adjust the silylation reaction by adding excess amounts of silylation agent to the silylation step, this is costly and often still does not lead the reaction to completion. Other attempts to drive the reaction further to completion have been tried by adjusting reaction conditions or process parameters in a reaction unit used in the silylation step. However, this is particularly problematic in continuous processes where the efficiency of the process requires a continuous feeding from upstream reaction units to downstream reaction units.
Another drawback of these processes is that the components in the produced silylated polymer composition that have unreacted reactive functional groups will function similarly to plasticizers. In this regard, they produce deteriorations in the mechanical properties of the silylated polymer composition, that would otherwise not be present or be present to a lesser degree. For example, the components with unreacted reactive functional groups cause a comparative reduction in tensile strength, shore hardness, elongation and modulus, relative to compositions without these unreacted reactive functional groups.
The unreacted reactive groups also contribute to variability in the produced silylated polymer compositions. This variability adds unwanted processing costs and losses for the manufacturer and for the consumer. It also results in unfavorable consumer opinions as consumers are likely to feel less confident that the produced moisture-curable silylated polymer meets their desired specifications.
Another approach has been to use scavenging agents to quench the unreacted reactive groups. However, many of these scavenging agents have low flash points and are consequently ineffective at the high process temperatures used in the process for preparing silylated polymers.
Silylated polymers produced by conventional processes often suffer other drawbacks as well. For example, the silylated polymer often suffers from color deterioration or a color change over time. This is problematic because this affects the performance of the polymers in some applications where particular colors or lack of color is important.
There remains a need in the art for a process for producing a silylated polymer without the drawbacks discussed above.